The major objective of these studies has been the application of physical and biochemical techniques to map and to define the structure of specific genetic regions in the genomes of both oncogenic and non-oncogenic human adenoviruses, with the ultimate goals of (1) relating these sequences to those biochemical activities which permit these viruses to influence or gain control of cellular functions (e.g., cell lysis and transformation) and (2) of defining basic mechanisms for regulation of genetic expression (e.g., initiation of DNA synthesis). A number of unique features have been described which may have implications in viral replication or carcinogenesis or both. Among these methods used are gradient sedimentation, molecular cleavage with restriction nucleases, gel electrophoresis, base sequence analysis, DNA cloning and electron microscopy.